Herein lies one of the problems with knitting. Most of the time when you finish a project, you have yarn left over. Sometimes it's almost a full ball, sometimes it's a few yards. I'm still not sure what the minimum amount of yarn left over is too little to keep. I've started to build up a collection of leftovers of all types of yarn, in skeins the size of my fist to the size of a ping pong ball. There are a couple of ways to deal with this problem. One is to find projects that use tiny amounts of yarn (such as Christmas decorations or baby socks or The Beekeeper's Quilt), but this can be difficult. Also, just because I knit socks for myself out of gorgeous hand wash only wool and am willing to put in the time to wash and dry them properly, doesn't mean that the mother (or father) of a new baby is going to want to hand wash baby socks. Even though they'd be super cute.
Another way to deal with the problem is so simple it's almost funny. Knit projects that use an entire skein of yarn, so you have no leftovers! Obviously you can't do this all the time, and honestly I often don't mind having leftovers of certain yarn. But when you only need one skein of yarn for a project, you can splurge a little and buy some extra special yarn, which is what I did when I found the pattern for the Destroyed Cowl. (This link requires a scribd account to download but it is also available on ravelry if you have a ravelry account.)
The yarn I used the first time around was Noro Kogarashi which is very unique. I have no idea what you would use it for if you had any leftovers, but it was great for this project and at around $22 per skein I was happy to only have to buy one of them. However when you consider that you can get a gorgeous hand-knit cowl for only $22, it's pretty much a bargain. It was a little scratchy/itchy at first but it softened a lot with blocking and multiple wearings.
This pattern is lots of fun to knit because it uses a few techniques that are fun to try if you haven't done them before, like the provisional cast-on,
dropping and making stitches,
and kitchener stitch.
Plus at the end when you've grafted both ends together you actually get to pull the dropped stitches apart on both sides of the cowl. Dropping stitches while you are knitting is usually a horrifying experience, so getting to do it on purpose is kind of a lot of fun.
And in between the first row and the last row is just stockinette so it's a great project to work on when you don't want to think too hard. The only thinking required is to make sure you leave JUST enough yarn for the last row and grafting the ends together. The first time I made this I think I ended up with about 12 inches of yarn. Which, even for my Mennonite sensibilities, is too little to keep. Problem solved.